Liberalism—both as a political current and an intellectual tradition—is mostly a modern phenomenon that started in the 17th century, although some liberal philosophical ideas had precursors in classical antiquity.
The Roman Emperor Marcus Aurelius praised “the idea of a polity administered with regard to equal rights and equal freedom of speech, and the idea of a kingly government which respects most of all the freedom of the governed”.
Scholars have also recognized a number of principles familiar to contemporary liberals in the works of several Sophists and in the Funeral Oration by Pericles.
Liberal philosophy symbolizes an extensive intellectual tradition that has examined and popularized some of the most important and controversial principles of the modern world. Its immense scholarly and academic output has been characterized as containing “richness and diversity,” but that diversity often has meant that liberalism comes in different formulations and presents a challenge to anyone looking for a clear definition.